Preparation and Characterization of Crystalline Thin Films Belonging in the Cu-In-S System for High Conversion Efficiency Solar Cells

本文对Cu-In-S体系晶体薄膜的制备和表征进行了研究，为高转换效率太阳能电池的研究奠定了基础。采用多源蒸发法在Si（001）硅片上生长薄膜。随着铟源温度的变化，CuInS_2、cuins_5s_8及其混合物的薄膜均外延生长。XRD和RHEED观察表明，CuInS_2薄膜不是黄铜矿结构结晶，而是c轴垂直于衬底的Cu-Au结构，并与闪锌矿结构共存。CuIn_5S_8薄膜结晶为取向良好的松弛尖晶石结构。XRD图中未发现CuIn_3S_5的存在。在500℃下沉积的富Cu CuInS_2薄膜结晶为黄铜矿结构，与Cu- au结构和/或闪锌矿结构共存。然而，在具有化学计量组成的薄膜中，没有发现黄铜矿相。在近20K温度下，首次测定了含黄铜矿相的500℃生长薄膜的光致发光光谱。除了供体-受体对发射外，还观察到弱和宽外子发射。光子的能量和发射的展宽被解释为不同晶体结构引起的不同发射的叠加。本文的研究结果对制备除黄铜矿结构外无其他相的CuInS_2薄膜具有一定的指导意义。

The preparation and characterization of crystalline thin films belonging in the Cu-In-S system were performed as the basic study for high conversion efficiency solar cells. The films were grown on Si (001) wafers using a multisource evaporation method.Thin films of CuInS_2, CuIn_5S_8 and mixture of these were epitaxially grown when the In source temperature was varied. XRD and RHEED observation showed that the CuInS_2 film did not crystallize in the chalcopyrite structure, but in the Cu-Au structure with the c-axis normal to the substrate coexisting with the sphalerite structure. The CuIn_5S_8 film crystallized in the relaxed spinel structure with fairly good orientation. No evidence of CuIn_3S_5 was found from the XRD patterns.The Cu rich CuInS_2 films deposited at 500℃ crystallized in the chalcopyrite structure coexisting with the Cu-Au structure and/or sphalerite structure. In films with the stoichiometric composition, however, the chalcopyrite phase was not found.The photoluminescence (PL) spectra of films grown at 500℃ including chalcopyrite phase were measured at near 20K for the first time. In addition to the donor-acceptor pair emission, the weak and broad exitonic emissions were also observed. The photon energy and broadening of the emission are explained as the superposition of different emissions caused by the different crystal structure.The results obtained in this study will be useful for the growth of CuInS_2 films without extra phases except for the chalcopyrite structure which have never been grown.